Improving your soil and plant growth with comfrey feed.

 Improving your soil and plant growth with comfrey feed.

Plant fertilisers such as Tomorite or Chicken pellets are getting increasingly costly to buy and sourcing suitable manure and transporting it to the farm is hard work. Increasingly at HCF we have become aware of the potential of growing our own fertiliser- Comfrey. When Andy Waterman first proposed growing it around the Old Fruit cage several years ago there was opposition from some team leaders, so we grew it in large pots for a few years before planting a small comfrey patch near the strawberry polytunnel. Demand for liquid fertiliser is increasing as are the potential uses and so the places where we are beginning to grow it are increasing.

Bocking 14 Comfrey 

Why is Comfrey so useful?

Leafy vegetables need lots of Nitrogen , Root vegetables need lots of Phosphorus (P), flowers and fruits need lots of Potassium (K). Or as Gareth Evans, my old Botany lecturer would say

“N for shoots, P for Roots, K for fruits.”

Comfrey is as good as Tomorite for plants such as tomatoes, peppers, and beans as well as greedy feeders like potatoes plus fruits such as strawberries, gooseberries and raspberries as the table shows.

In addition, it compares well with manure and compost:

One square metre will produce around 7 kg of comfrey a year which can be cut three or four times during the season and so a large biomass of plant material can be produced from a small space. The wonderful benefit of Comfrey is that it has extremely long roots which can mine nutrients from several metres below the surface and which would otherwise be totally unavailable to vegetable crops. The disadvantage is that once comfrey is growing the roots are difficult to kill off and the plant lasts for over 20 years. So don’t ever plant comfrey in a place if you might sometime later want to move it somewhere else.

How to grow comfrey.

We use a variety called Bocking 14 (developed in Bocking, Essex) which is a sterile hybrid clone of two Russian forms. Bocking 14 doesn’t set viable seed, but does spread slowly if not checked back. To make more plants a plant is cut up, the leaf removed and the stem and upper area of the root cut into small sections a few centimeters long.These are allowed to grow roots and leaves in a pot containing a light compost. The young plants are planted out into a cleared area of ground where they are expected to grow. Planting distances are approximately 60 cm between plants.

Comfrey growing along a fence line made of old pallets

How to use comfrey

There are several ways to use Comfrey.

Rotting comfrey at the bottom of a bucket

Toby Turl has recently introduced a new method of makes a concentrated liquid feed. He cuts the leaves and puts them in a bin with a hole at the bottom. As the comfrey breaks down liquid drains through the hole into a small container below which collects the concentrated liquid. He makes a litre every couple of weeks and this is diluted about 10 times over before being watered on plants.

Adding comfrey to a compost bin to speed up composting

I cut comfrey leaves, mixing them with pernicious weeds (nettles, couch grass, docks, dandelions and thistles) and toss them into a sack in an old rubbish bin which has been filled with water. After a few weeks when I need some liquid feed I push my watering can into the bin, draw up half a can full of liquid, dilute it further with water and pour onto my fruit bushes. After a couple of months all the comfrey and weeds have broken down in the sack, so I draw out the liquid for use on the plants then tip the completely dead slime into the compost bin or onto a plot. This is a much speedier method than cold composting and there are no viable seeds or pieces of root which will find their way back onto the soil.

Another use for comfrey is as a surface mulch on blackcurrants and raspberries. I use the “chop and drop” method. First chop your leaves, then lay a 5 cm mulch of the leaves on the soil around the plants. Within a couple of weeks the leaves will have gone black and within a month they will have disappeared completely. This mulch slows down evaporation of moisture from the soil and suppresses weeds. As the comfrey leaves wilt they attract slugs and snails, possibly from feeding on surrounding valuable plants and so reduce damage. Hopefully then, the slug will be devoured by a hungry ground beetle or blackbird.

So there are several ways in which we can use this most helpful of plants on our community farm.

More lessons learned from our visit to Charles Dowding's NO-DIG garden

We learned a lot from observing and reflecting on the practices of Charles Dowding in Somerset. As well as being useful on our plots these tips might be helpful for those stakeholders who have gardens at home.

New ground coming into cultivation - the NO-DIG method.

If you have a weedy patch (like a new allotment or neglected area) that you wish to bring into cultivation, rather than put in lots of effort into digging and weeding why not follow Dowding method? First spread a thin layer of spent hops to encourage the worms. [If you can't get spent hops, why not try a mixture of grass cuttings and pondweed?]. Then cover with large sheets of cardboard (from bike shops or supermarkets).  Put a 3 in layer of spent hops on top of the cardboard. Monitor for 6 months and hoe off any weeds that make it through the cardboard

If you began this process in the autumn by late May/June you can plant pre sown plants through the hops and cardboard - plants such as courgettes, squash, pumpkins - to get an autumn harvest.

Following on from this you can monitor for weeds through the next winter. Then the following Spring rake away what is left of the hops and cardboard and put on the compost heap. Pull out any persistent weeds. Cover with a 1in layer of compost and its ready for a normal season of sowing. Again you don't have to dig, just plant in modules grown in the polytunnel.

Weeding in a standard plot - the NO-DIG method

 You need to keep on top of weeds. Ideally take them out when they have just germinated and are small. Dowding does 2-3 "weed strikes" in March and April using a swivel/oscillating hoe in the surface compost, to kill small seedlings.  If you miss them in April pull them up whenever you spot them on your plot. Don't ignore the weeds on your plot even if you are concentrating on a different crop in a different area. You really shouldn't have weeds that are flowering on your plot. If you let them set seed you are building up problems for your team in subsequent years.

Notice the organic matter in the mulch that has been added
and the weed free nature of the soil

Edges - the NO-DIG method

Keeping on top of edges is more work for Dowding than weeding. He has a good sized valley at the edge of the footpath to prevent the bindweed and couch grass creeping in from the path. He trims the edges every 3-4 weeks with long handled shears and removes the clippings. Adjacent to his polytunnels he has an edge about 50 cm away from the polytunnel and keeps it clear of weed by growing quick growing lettuce or radish there to ensure that he is weeding these areas and preventing couch and bindweed getting into the polytunnel.

Notice how Dowding clears the weeds and grass from the edges of his polytunnel and keep the weeds down by growing quick maturing vegetables

Pests -- the NO-DIG method

According to Dowding slugs like rotting brassica leaves because they contain a form of alcohol. (That is why beer traps work!). Minimise slug habitat by keeping path edges short and neat and removing lower leaves of brassicas before they yellow. Dowding claims that alcohol is a by-product of anaerobic fermentation which develops when organic matter breaks down in the fairly anaerobic conditions of dug soils. He claims that no dig helps reduce the amount of alcohol in the soil (which is what the slugs like) because all the organic matter breaks down on the surface where there is more oxygen and none is dug into the soil.

By removing the older leaves from the Cavolo Nero there is nothing breaking down which would provide alcohol for slugs and so they are almost absent from no-dig beds

Please let all of us know if you are going to try any of these NO-DIG methods on your plot.

How organic matter breaks down in the soil to make humus:soil carbon pathways

When plants and animals die in the soil the soil organisms such as earthworms, woodlice, slugs, snails as well as the bacteria and fungi use the organic matter as food. The carbon in dead plants and animals is broken down in a number of different ways but two main stages are evident:

1.      the cellular structure and recognised organic substances and minerals in the decomposing organism disintegrate and become unrecognisable as big molecules are broken down to smaller ones.

2.    

           totally new combinations of these broken-down products develop. It is defined as humus when it becomes impossible to distinguish what the original material came from. So humus is an amorphous mix of black or brown gel-like substances of high molecular weight modified from the original tissues by various soil organisms.

There seem to be two main methods by which humus is made in soils

Process 1. The decomposition of organic materials such as cellulose and starch from crop residues and manure. Soil invertebrates eat detritus (dead plants and animals) and make the particles smaller for bacteria to work on, first by breaking them down, then by building them up slowly into humus. An alternative to this is the decomposition of woody organic material such as lignin in crop residues and compost by white rot fungi. Then the products are eventually built up by bacteria into humus.

Organic matter decomposition and formation.  Ankush J

Process 2. Carbon compounds which have been exuded by plant root are used by certain soil fungi which produce mycorrhiza. These form a symbiotic relationship with plant roots. The mycorrhiza use these sugar exudates to make glomalin, a major component of decomposing organic matter and this will eventually be built up into humus.

The process of humus formation through decomposition of organic matter is not very efficient at building humus in soils. Of 100 g of organic matter that is added to the soil maybe 60-80g will be converted back to carbon dioxide by the invertebrates and the bacteria, 3-8 g will be taken up by bacteria to help them to grow, 3-8 g used to make other plant organic compounds and possibly 10-30 g used to make humic compounds.

It is known that around 40% of the sugars made by photosynthesis in plants leaks out of the roots. This can be used by mycorrhizal fungi, some of which invade the plant roots. These fungi supply many nutrients including up to 90% of the plant's nitrogen and phosphorus requirements, plus calcium, potassium, magnesium and iron, as well as essential trace elements such as zinc, boron, copper, cobalt, molybdenum and manganese. They often supply water as well - all in exchange for liquid carbon! (Smith, 2008). So these mycorrhiza effectively increase the coverage of the plant’s root system in the soil and can make the plant much more efficient at absorbing plant nutrients (particularly phosphate) from the soil solution.

Mycorrhizal hyphae colonising the roots of a pine seedling. 

As the mycorrhiza grow they produce a protective surface coat of glomalin, a glycoprotein (protein containing a plant sugar). The glomalin drops off into the soil where it acts as a "super glue," helping sand, silt and clay particles stick to each other as pea sized lumps called aggregates. The small spaces between the aggregates help rainwater to move through the soil more easily. Moisture is absorbed in these aggregates which is protected from evaporation, but the mycorrhiza are able to access this water and supply it direct to the plant roots at times of water shortage. It is substantially due to the gel-like substance of glomalin that it is often stated that 1 kg of humus can hold 4-20 times its own weight of water. And it helps us to understand that soils rich in humus will have a good structure, improved water holding capacity, enhanced infiltration and drainage and enhanced nutrient exchange capacities

Glomalin also stores approximately 25-33% of the total soil carbon and can last in the soil for 7-40 years as part of the soil active fraction.  At some stage the glomalin is either respired to carbon dioxide if the soil is dug, or is converted to humus if the soil is not dug and there are plenty of mycorrhizal fungi in the soil.  

It seems that the process of making humus in soils through the activity of mycorrhizal fungi in process 2 is more efficient than soils which make humus by process 1 because soils that have not been dug generally have higher humus levels.

Another benefit of soils which have abundant mycorrhiza, glomalin and humus is that they have a markedly increased resistance to climate variability.

HCF's has a policy of feeding the soil by adding lots of animal manure and as much compost as is available. However as this article suggests this method is not very effective at converting soil organic matter to humus and may not actually increase soil carbon levels if other farming practices such as digging and leaving the soil bare destroy soil carbon.

Most of the cultivated plots at HCF are likely to be acutely short of mycorrhiza as digging or rotivating breaks up the hyphal strands and disrupts their relatively slow growth. Furthermore our practice of leaving the soil bare and plant free for several months of the year means that during this period the mycorrhiza have no living plants to exchange nutrients with and so decline. One of the challenges for us at HCF is to work out how we can help to develop mycorrhizal growth in the vegetable plots. Maybe we should think more clearly about planting winter cover crop?

References

Organic matter decomposition and formation.  Ankush J

Mycorrhizal hyphae colonising the roots of a pine seedling. Aberdeen mycorrhiza Research Group

What is soil organic matter?

Soil organic carbon is organic matter is made up of living organisms, undecomposed plant, animal and micro-organism residues and humus, formed over many years. You cannot have good soil structure without high levels of organic matter. It is the main food reserve for living soil organisms and many of them provide the simple substances that are taken up by the plant roots. The most reliable method of finding out the soil organic matter (SOM) concentration of a soil is by burning (dry combustion) at temperatures of over 900⁰C. The result is normally given as percentage organic matter in the soil. Farmers weekly provide a simple chart for farmers to score the quality of their soil.

Less than 1% very low

Less than 2% low

Less than 4% Medium

Less than 8% High

Over 8% Very high

Typical components of a soil

http://www.cartage.org.lb/en/themes/sciences/botanicalsciences/PlantHormones/PlantHormones/soil.gif

Organic matter is made up of three main components which have been called the living, the dead and the very dead!

Living organisms, plants, animals, soil invertebrates, bacterial and fungi are all considered to be part of soil organic matter, and they play a big role in contributing organic residues to the soil and in formation of more stable types of organic matter. Up to 15% of soil organic matter is living organisms and fresh organic material.

Figure 2 The structure of soil

Active soil organic matter is primarily made up of freshly dead plant and animal residues that break down in a very short time, from a few weeks to a few years. It is sometimes called detritus if it contains partially broken down cells and tissues that are only gradually decomposing. One third to one half of the SOM is active soil organic matter, the detritus of partially and slowly decomposing plant and animal material that may last decades.

Stabilised or passive soil organic matter, is known as humus. It is very dead(!) and not biologically active because it provides very little food for soil organisms. Humus may take hundreds or even thousands of years to fully decompose! Humus is very important as (a) it acts like a sponge and can absorb 4-10 times its weight in water,  (b) it is a way of taking carbon dioxide out of the atmosphere and burying it in the ground (sequestering it) and so helps to mitigate the effects of rising CO₂ levels.

Soil organic carbon from
http://soils.usda.gov/sqi/concepts/soil_biology/images/soil_f1_high_res.jpgaption

Soil organic matter may enter the soil in a number of ways, such as addition of manure, compost, mulch such as sweetcorn stalks or woodchip, leaf mould, coffee grounds, eggshells, chicken pellets or the growing plants in their little pots of compost. But it may also be produced in the soil by the crop and the surrounding weeds and soil animals grow and then die and remaining in or on the soil surface.

Soil organic matter may be removed from the soil when crops are harvested, often with some sticky soil around them, on our boots, when the wind blows it away, or heavy rain washes or leaches it away through the soil.

The global climate is becoming more unstable due to global warming. Last year it was "the Beast from the East" for us at HCF, followed by a warm and fairly dry summer. Who knows what it will be this year? One of our aims at HCF should be to create a soil that is as resilient as possible to climate change. To be this soil it needs high levels of Soil Organic Matter. This soil will be able to hold more moisture, which, among other things, will enable it to cope with longer periods of water shortage or heavy and excessive rains which would otherwise cause leeching or runoff. 

Refs

http://www.cartage.org.lb/en/themes/sciences/botanicalsciences/PlantHormones/PlantHormones/soil.gif
http://soils.usda.gov/sqi/concepts/soil_biology/images/soil_f1_high_res.jpg

Creating a healthy soil at Highbridge Community Farm

Climate change and the ethos of HCF

Most of us are familiar with the broad issues of climate change; an increase in atmospheric carbon dioxide (CO₂) concentration from 278 ppm in the preindustrial period (circa 1750) to 405.5 ppm in 2017; an increase of the greenhouse gas methane from 722 ppb to 1859 ppb in the same period, an increase in nitrous oxide from 270 ppb to 330 ppb in the same period. (Lal, 2019) This has already raised global temperatures by over 1⁰C since the Industrial Revolution with dire consequences as exemplified by the increase in frequency of extreme events throughout the world. Furthermore there is the real likelihood that we will miss the target set at the Paris Climate Conference (COP 21) in 2015 of limiting global warming to 1.5⁰C. (IPCC (Intergovernmental Panel on Climate Change, 2018)

The Highbridge Community Farm ethos (HCF) statement says "We have evolved from the Transition Movement and retain their founding principles - a community-led response to the pressures of fossil fuel depletion and climate change, supporting local economies and moving towards a more viable and sustainable future.  Now a mutual benefit co-operative society in our own right, we work together to produce food for ourselves with minimum use of fossil fuels and chemicals.  We support growing techniques that maintain the natural balance of the soil, preserve wildlife and their habitats, and encourage biodiversity.

Over the nine years of our existence our aim has been to grow good organic food. We have managed the soil to obtain good crops, without ever really addressing the issue of how to  improve the health, fertility and productivity of our soil in an environmentally sustainable way.  Ideally this soil should be resilient to be able to cope with whatever crop is planted in it and cope with whatever combination of weather events that is thrown at it. Probably the best measure of soil health and resilience is one with a high organic carbon content. This is in line with the Climate Accord proposed in Paris in 2015 which initiated the 4 per 1000 programme of raising Soil organic carbon (SOC) in world soils at the annual rate of 0.4% per year to a depth of 40 cm. (Chambers, 2016)  The UK signed up to this initiative and Environment Secretary Michael Gove has undertaken to deliver on this ambitious goal by supporting soil health improvements in the UK. (Eldridge, 2018)

There is an added benefit of raising SOC; the potential lowering of atmospheric CO₂ on a worldwide basis by raising SOC is approximately 84 ppm of CO₂. This burying of SOC in the soil in the form of humus is called sequestration. So raising SOC at HIghbridge Farm will be a win:win. We can play our part at HCF to produce a better, more resilient and productive soil and our efforts will benefit everyone if global CO₂ levels fall!

What is a healthy soil?

Dr F Crotty states "Soil health can be defined as a soil's ability to function and sustain plants, animals and humans as part of the ecosystem." She identifies five main factors that impact the health of the soil and can have a large influence over its capability and resilience to function; they are:

1. Soil structure
2. Soil chemistry
3. Organic matter content
4. Soil biology
5. Water infiltration, retention and movement through the profile (Crotty, 27 July 2017).

Farmers tell us that a good soil

·         drains well and warms up quickly in the spring

·         does not crust after planting

·         soaks up heavy rains with little runoff

·         stores moisture for drought periods

·         has few clods and no hardpan

·         resists erosion and nutrient loss

·         supports high populations of soil organisms

·         has that rich, earthy smell

·         produces healthy, high quality crops and grass

·         are easy to work in a range of conditions.                                                                                                 (LEAF -LInking Environment and farming, 2016)

How is our soil doing for earthworms?

Earthworm survey of soil quality 30.3.19

In early February and March 2018 Dr Jackie Stroud, a Natural Environment Research Council Soil Security Fellow at Rothamsted Research, led and co-ordinated a project to study the worms in farm soils. A total of 126 farmers took part. Participating farmers volunteered to dig 10 pits, each 20 cm x 20 cm x 20 cm, in one field. They counted the number of adult worms in the sample. Adults are identified as those having a saddle on their bodies. The total number of worms were counted, then the juveniles returned to the soil. An identification guide allowed them to allocate any sightings to one of the three main types of earthworm. The adults were then split into small surface red ones (epigeic), small or medium pale worms which were grey, pink or a darker green (endogeic) or larger pencil sized worms which were heavily pigmented red or black (anecic).

Each of these worm groups has a different function. The epigeic surface worms breakdown surface litter and are a good source of food for native birds such as thrushes and blackbirds. The endogeic topsoil worms mix soil and mobilise nutrients for plant uptake and so support plant productivity. The anecic, deep burrowing large worms are the drainage worms which can form 2 metre vertical burrows which help with water infiltration and deep plant burrowing.

On Saturday 30 March 2019 we conducted the same experiment over our ten plots, with a few teams adding a second count. Here are all our results

Earthworm Sampling at HCF 30.3.19

Plot	Total worms	Epigeic worms	Endogeic worms	Anecic worms	Grown last year	Manure added in autumn?	Compost added in autumn	Roto- Last year	Roto - this year	Plastic over winter
2	14	0	3	0	Brassicas	No	No	No	No	No
4	15	5	3	1	Fennel	Yes	No	No	No	No
6	7	0	6	1	Parsnips	Yes	No	No	No	No
8	30	2	5	0	Broad beans	Yes	No	No	No	No
10	7	0	6	1	Potatoes	No	No	Yes	No	Yes
12	0	0	0	0	Onions	Yes	No	No	No	Yes
14	31	0	4	5	Potatoes	Yes	No	No	Yes	Yes
16	4	0	2	0	Onions	No	No	No	No	Yes
18	16	1	4	0	Potatoes	Yes	No	Yes	Yes	Yes
20	13	1	1	0	Carrots	Yes	No	Yes	No	Cardboard mulch
Total	141	9	37	9
No of plots with worm	9	4	9	5
Fruit	3	0	3	1	Rhubarb	Yes	No	No	No	No
1	15	0	4	0	Squash	No	No	No	No	No
11	2	0	0	0	Potatoes	Yes	No	No	No	Yes
3	13	1	8	0	Sweetcorn	Yes	No	No	No	Sweetcorn mulch

How do our results compare with Dr Stroud's research for 126 farms? Dr Stroud analysed the results she obtained from farmers on 5 counts:

(a) Total number of soil pits with ≥1 earthworm (juveniles or any adults below),

She found that the average field had 9 earthworms per spadeful,

We found an average of 14.1 worms per count

(b) Total number of soil pits with ≥1 adult epigeic surface earthworm.

She found that 21% had no sightings of these worms and 42% of fields had very few. These worms were significantly less likely to be found in fields that had been tilled (ploughed or dug). Low numbers in a field suggest a lack of surface litter which earthworms can pull into the soil.

We found that 6/10 of our plots had no epigeic worms and a further 3/10 had very few.

(c) Total number of soil pits with ≥1 adult endogeic topsoil earthworms.

She found that 67% of fields had good presence of these worms.

We found that 9/10 of our plots had >1 adult endogeic worm. Endogeic topsoil worms mix soil and mobilise nutrients for plant uptake and so help to raise crop productivity.

(d) Total number of soil pits with ≥1 adult anecic deep burrower worm.

She found 16% of these fields had none of these worms and a further 23% had 1 or 2 out of the 10 samples that were examined that had these deep burrowing worms.

We found that 6/10 plots had no anecic worms and another 3/10 plots had just one anecic worm.

The lack of anecic worms was of concern to Dr Srroud because they are 'drainage worms' with vertical burrows that aid water infiltration and help stop fields getting waterlogged. The deep-burrowing worms have slow reproduction rates so recovery in their populations could take a decade under changed management practices. Deep burrowers may not always be in the topsoil, so it is important to look for pencil sized vertical burrows at the bottom of the hole of a pile of straw or stones on the surface (a midden) which overlies a vertical burrow. If these are observed then we recorded that an anecic worm has been observed.

(e) Total number of soil pits with high numbers (≥ 16 earthworms per pit, ≥400 earthworms per m²) of earthworms (total number including all juveniles and adults). She found that one in 10 fields had more than 16 worms per spade. Top fields had around 27-30 worms per sample.

We had an average of 14.1 worms per pit which gives us an estimated 353 worms per square metre. Only two of our plots reached “top field” numbers of worms.

Dr Stroud concluded that 42% of fields had sub-optimal numbers of worms (defined as <10% presence for at least one ecological group) and may be "overworked" leading to absence or scarcity of surface dwelling and deep-burrowing worms. Only 15% of fields had a good presence of all three groups. Her results indicate that tillage is likely to reduce the numbers of surface and deep burrowers first. This may help explain the alarming decline of the song thrush which often feeds in fields on these worms. Topsoil worms are generally least affected by over-cultivation.

What do you think we should conclude about our results? Clearly they are just a snapshot, giving us a baseline for further monitoring. Our results may have been affected by dry weather the previous week, but we can expect the worm numbers in the top 20cms to fall further as the weather warms up. Should we do more repeats on the plots surveyed? Should we do studies on the other plots? Should we be thinking of changing our soil management practices in the light of these results?

I should be really grateful if you would write your comments, observations and thoughts below, so that we can have a dialogue about how we are caring for the soil at HCF.

Refs
J L Stroud Soil health pilot study in England.: Outcomes from an on-farm earthworm survey. 2019  https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0203909    Viewed online March 2019